[dredmorbius]

I've been looking into synfuels, especially petroleum analogs, of which there's been over 50 years of research.

I do find it genuinely exciting. The same benefits of petroleum (safety, stability, portability, storage, and very, very flexible use) apply to any synthetic analogs.

The "problem" is that you pay full cost. Most synthesis methods lose about 50% of the input energy (mostly in hydrogen electrolysis). Where petroleum has historically offered 100:1 energy benefits, and is now typically delivers 20-30x the input energy, synfuels would cost you energy: 1:2 or worse. The equivalent energy cost increase is 40-60x that of present sources. That's not objectively a bad thing, but it's a tremendous shock to a system based on cheap energy.

The research as I said is impressive: Brookhaven National Laboratory (US), M.I.T., and the US Naval Research Lab, going back to Meyer Stienberg at BNL in 1964 (the suggestion itself came from M. King Hubbert, who'd first projected peak oil, in a 1963 paper). Progress, however, has been fairly scant, with only very small-scale tests.

The advantage would be a fuel that's infinitely miscable and substitutable for existing petroleum-based petrol, diesel, kerosene (a/k/a jet fuel), etc. And it can be carbon-neutral (via seawater or atmospheric-based carbon stocks). The disadvantages are cost and complexity as well as input energy. That said, I think it's well-worth pursuing.

[cpprototypes]

The energy efficiency of the process is bad, but the future economic conditions could change dramatically:

1) Fossil fuels costs will eventually start rising and never come down again. How much investment and attention will synthetic production receive when oil is $100/barrel? Or at $200/barrel, or $300/barrel? More investment could lead to significant process improvements.

2) Solar energy has improved tremendously and continues to improve more. But the great weakness of solar is that it's only effective at daytime. Anything produced in excess of daytime demand is basically waste energy. Since it's waste energy, the inefficiency of the oil synthesis process doesn't matter. The only competitor here is other energy storage methods such as batteries. The key question here will be, is it better to store this excess waste energy in batteries or use the synthetic process to make oil? From a pure efficiency standpoint, battery is better. But when considering the existing oil infrastructure, the answer is not as clear.

[dredmorbius]

The breakthrough cost is key.

One of my recent thoughts is that it's not so much that renewables are expensive as that fossil fuels are insanely under-priced, though that gets into a pretty deep economic question of just what price and cost are supposed to be.

For electrical generation, the problem with a fuel-based intermediary storage is that the net efficiency is quite low: 50% loss at fuel formation, at best 45% efficiency from thermal generation (Carnot's Law is a bitch). Fuel cell tech might offer an out, but the catalysts are rare and expensive (though if we can find an all-platinum asteroid out there, solar + synfuel + space-mined catalyst might offer advantages).

Solar costs have fallen, but the efficiency is capped. Moreover, as panel costs fall they're dominated by less-fungible elements, mostly installation and maintenance. There's the 20-year life (multiple systemic decay pathways) which means you need to replace 5% of your total stock every year.

I'm not arguing against solar, but rather, against an abudant-energy future. Even with energy issues addressed, many other factors, including literally dirt (well, topsoil), challenge humans.

Leibig's Law of the Minimum is another bitch.